What is the best EPUB reader?

After evaluating a number of EPUB readers available in Apple Store and Android Market, basically none of the available EPUB readers fill all my requirements. The situation on Android is especially bad, with many apps filled with advertisements, slow in performance and unstable.

Yet, if you are using Apple, iBooks and NeoSoarBook are comparatively better options.

On Android, among the many EPUB reader apps, I found one named "Lithium EPUB Reader", which is quite promising in delivering the features that we need - https://play.google.com/store/apps/details?id=com.faultexception.reader&hl=en

It's ad-free, with easy to use annotation function. I especially loves its clean interface and pop-up link references boxes, which shows link references as message boxes. Down side, it's a bit slow in performance.

Or, another option is to use the PDF format. The down side, of course, is the lacking of links to scriptures and references.

If you have used any EPUB app that you think is good to recommend to others, please let me know.